Recently, scientists at the Vienna-based Institute for Quantum Optics and Quantum Information (IQOQI) developed a universal method that has a high chance of successfully inverting the evolution of a qubit. This Physical Review Letters protocol can propagate any target qubit back to the state it was in at a specific point in the past.
The development of this protocol builds on a prior paper from the same team that was published in 2020 and featured a number of time-translating protocols that could be used in uncontrolled environments. Even though some of these protocols showed promise, it was discovered that they had a too low chance of success in the majority of the scenarios that were tested. So, in their latest study, the researchers sought to develop a different protocol with a higher chance of success.
One of the researchers who conducted the study with Benjamin Dive, Miguel Navascués, and David Trillo said, “Our newly developed protocol inverts the unitary evolution of a qubit,” according to Phys.org. “A qubit (or quantum bit) is a two-level quantum system that functions as the quantum counterpart of the bits used in quantum computers. When designing physical processes around a quantum system, one must take into account or at least control any inherent temporal evolution (e.g. g. to create a quantum computer). Our protocol takes a qubit and outputs the same system, but in the condition that it would have been in if it had evolved backwards in time. “.
“Our protocol works for uncontrolled systems, or qubits on which we don’t know how to apply specific transformations.”
David Trillo, one of the researchers who carried out the study .
The protocol developed by Trillo and his coworkers is universal, i.e., it can be applied to any qubit, no matter how it evolves naturally over time or in what state it is in when the protocol is applied. The success of universal protocols has a certain probability because they are inherently probabilistic; they cannot succeed always.
The researchers discovered that their universal quantum rewinding mechanism has a high probability of success, or 1. In essence, the protocol operates by superposing a target qubit’s flight paths and then carrying out a series of quantum operations on it.
Trillo explained that “our protocol works for uncontrolled systems, or in other words qubits on which we do not know how to apply particular transformations.”. “Its cool new feature is that whenever it fails, we can fix the issue and get the system back to where we want it to be. We can increase the probability of success to the desired level by adaptively applying these corrections, but at the expense of the protocol’s running time. “.
With the new universal protocol developed by Trillo and his coworkers, there is a good chance that researchers will be able to rewind any given qubit in an uncontrolled environment. Although there were already protocols that could accomplish this in controlled environments, being able to propagate individual qubits in uncontrolled settings to a previous state could open up new, beneficial research opportunities.
Trillo continued, “One wonders what other phenomena from the controlled setting we can transfer to a controlled one.”. “Ideally, we would like to apply this protocol to higher dimensional systems. But given that new approaches are required, this seems to be quite a challenge. In the original paper’s other protocols, particularly the SWAP protocols, we are also attempting to increase their likelihood of success. “.
More information: D. Trillo et al, Universal Quantum Rewinding Protocol with an Arbitrarily High Probability of Success, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.110201
